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Auto Racing/Valve Clearance

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Expert: - 6/5/2007


Question
why is that the exhaust valve/ intake valve are not of the same size; one is bigger than the other. Why don't they have the same valve clearance?please explain.

Answer
Well- -  for one thing , your engine takes IN a mixture of gas and air, then burns the gas, so there's actually less volume left.  That sounds silly and probably is, but all engines are that way and the difference is usually about 20%.   Of course, the intake mixture is drawn in by vacuum, and the exhaust is forced out by the rising piston .  It sounds like I really can't answer that question accurately. It's something I've been curious about but never thought to ask .   Good one !!! you've stumped me !  But I WILL find out ! Look for a follow up answer.

Dan Liddy
Sarasota, Fl.  

Auto Racing

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Dan Liddy

Expertise

Anything concerning race cars, 20 years competition experience, Senior Competition Driver Instructor , car builder, mechanic, welding, fabrication, tuning , engine modifications, set up, suspension design. Specializing in Datsun/Nissan products. Please submit questions about RACE CARS ONLY. No street cars, no video game scenarios Thank you.

Experience

I have been racing for 20 years, I have been the Central Florida SCCA Regional Championship points for 5 years running, and won the championship in my class 2 times. During my first start in the 60's I won many solo awards and the State Championship Drags. I serve as a senior instructor for SCCA, and have taught in Mercedes AMG events at Daytona, and Dodge Viper Days at Sebring International. I have been in the thick of the competition for all of my career. At one time or another I have driven race cars at speeds nearing 195 MPH. It's quite a ride !

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